The most common method of skin tanning involves the process of exposing skin to ultra-violet light. Health research has shown that both the condition of under-exposure to ultra-violet light and the condition of over-exposure to ultra-violet light causes a variety of health problems. Health research has also shown that specific ranges of wavelengths of ultra-violet light are responsible for producing health benefits. Moderate exposure to specific wavelengths of ultra-violet light produces the greatest benefits with the least amount of health risk. Certain methods and devices are useful at controlling the quantity and quality of ultra-violet light exposure in the effort to produce the greatest health benefits with the least amount of health risks. Ultra-violet light quality depends primarily on the ranges of wavelength of ultra-violet light; where the highest ultra-violet light quality is the ultra-violet light that produces the greatest net health benefits.
The sun is a primary source of ultra-violet light for tanning. The quantity of light exposure to the sun is simple to control. The quality of ultra-violet light exposure by the sun is not simple to control. Lamps that provide alternative sources of ultra-violet light allow for tanning services that do not rely on the sun. These tanning services are available and are administered in a controlled environment such as in personal care service salons. The industry providing controlled exposure to artificial ultra-violet light is generally referred to as the “indoor-tanning” industry. Indoor-tanning does not implement systems that are directly dependent on the sun as the source of ultra-violet radiation. The quality of the indoor-tanning ultra-violet light has become important in differentiating services available within the same indoor-tanning salon and between competing tanning salons.
Light with wavelengths in the ultra-violet range is often referred to as UV light or UV. UVA, UVB and UVC describe three separate non-overlapping but adjacent ranges of light fully encompassing the UV light range. The range of light referred to as UVA generally has the longest set of wavelengths within the UV range and includes wavelengths between 290 and 400. UVA-1 is between 340 and 400; UVA-2 is between 290 and 340; and UVA-3 is between 290 and 310. The range of light referred to as UVC generally has the shortest set of wavelengths within the UV range and includes wavelengths between 160 and 260. The range of light referred to as UVB includes wavelengths between 260 and 290.
The use of the terms UVA, UVB and UVC allow the various properties of UV light to be categorized in general ways. UVA has the best capability of tanning skin. UVB does not produce a tan in the third layer of skin. UVC light does not produce a tan but can sterilize some biological agents such as certain bacteria. Under certain conditions UVB will tan the second layer of skin. The second layer of skin when tanned with UVB has a shedding period of 5 to 8 days. Skin tanned with UVA only has the third layer of skin tanned which results in a normal shedding cycle of 28 days.
Under normal conditions the outer layer of skin, also known as the first layer, is composed of dead cells. Normally, dead cells will not produce melanin upon exposure to moderate amounts of UV. The layer under the first layer of skin is referred to as the second layer of skin, and is composed of active cells that may be functioning in some biological manner and will produce melanin upon exposure to UVB light. UVB skin tanning has, what some tanners consider, an additional negative effect, UVB tanning will thicken the second layer of skin and as a result increases the visibility of skin lines and wrinkles. UVB tanning creates a shedding cycle of 5 to 7 days which is undesirable when a UVA tan has a shedding cycle of 28 days. When UVB is combined with UVA the shedding cycle of the UVA tanned layer is accelerated since the second layer is shed more quickly and the third layer becomes the second layer as a result and is shed within another 5 to 7 days.
Under normal conditions the layer of skin that will produce melanin when exposed to UVA light is referred to as the third layer of skin. In exceptional conditions such as albinism, the third layer of skin is not capable of producing melanin. For the purposes of this application, albino skin is considered an exception to the norm and will not be referred to as a third layer of skin but as an albino third layer of skin.
It is common knowledge that all wavelengths of UV over long exposure periods damages the skin in various ways. Therefore, it is desirable to limit the exposure of UV radiation to skin. Alternatively, some UV exposure is generally considered necessary in order to maintain good health in other bodily functions, such as the generation of vitamin-D. Vitamin-D is useful in the absorption of calcium in the body. Therefore, it has been recommended by various health organizations studying the phenomena that moderate exposure to UV light has a net health benefit, whereas over-exposure or under-exposure of UV results in a net health deficit. The art of indoor-tanning to remain useful should provide for ever increasing controllability of the application of the light therapy. As a light therapy tanning should be applied with specific goals and procedures to maximize the benefits of the therapy.
For people desiring a tan, the main benefits of UV exposure is the production of tanned skin. Tanners enjoy positive psychological and perceived positive social benefits resulting from having tanned skin. In order to limit the total amount of UV radiation tanners are exposed to while maintaining a tan, it is desirable to reduce as much as possible the exposure to UV light outside the UVA wavelength range. UVB and UVC wavelength ranges of radiation are by definition not capable of tanning skin with a 28 day shedding cycle and therefore reasonable efforts should be made to eliminate UVB and UVC from the source of light tanners are exposed to.
Indoor-tanning methods generate UV light from converting electrical energy to light within devices such as UV fluorescent bulbs and high and low pressure mercury vapor bulbs are two specific types of light bulb technologies. UV light bulbs currently in use have properties of high voltage, high temperature, and low electrical energy to UV conversion efficiencies under seventeen percent.
Within the fluorescent light bulb category there are a variety of types that differ mainly in the percentage of UV light produced in the UVA, UVB and UVC wavelength ranges. For tanners concerned with overexposure to UV light the more desirable fluorescent bulbs have a higher percentage of light in the UVA-1 wavelength range. Tanners concerned with overexposure prefer and tend to pay a premium for tanning services that have the least amount of UVB and UVC.
Depending on weather conditions, typically 88% of the UV radiation from the sun is UVA, in this case an artificial source with more than 88% of the UV radiation is UVA is considered a safer tanning method than sun-tanning. Common fluorescent tanning bulbs and associated services have UV composed between 92.0% UVA to 97.5% UVA. Currently, high pressure quartz metal-halogenide bulbs have in general 98.5% UVA and are considered to be the least harmful artificial tanning bulbs currently used in indoor-tanning salons.